The overall objective of this project is to gain a sufficient knowledge of the ecology of arboviruses to allow the development of effective disease control programs. The objective will be accomplished by a study of alternative means by which arboviruses overwinter in a temperate area, and a study of genetic and environmental factors that influence the competence of mosquitoes to be vectors. The procedure will be to develop laboratory models and methods for studies of these problems and to extend these studies into the field where the encephalitis viruses and endemic and where alternative methods are needed to replace the present use of insecticides to control mosquito vectors.